package com.kylin.rw;

import sun.awt.windows.ThemeReader;

import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;

/**
 * 独占锁（写锁） 一次只能被一个线程占有
 * 共享锁（读锁） 多个线程可以同时占有
 * ReadWriteLock
 * 读-读 可以共存！
 * 读-写 不能共存！
 * 写-写 不能共存！
 */
public class ReadWriteLockDemo {

    public static void main(String[] args) {
        //MyCache myCache = new MyCache();
        MyCacheLock myCache = new MyCacheLock();
        for (int i = 1; i < 10; i++) {
            final int temp = i;
            new Thread(() -> {
                myCache.put(temp + "", temp + "");
            }, String.valueOf(i)).start();
        }

        for (int i = 1; i < 10; i++) {
            final int temp = i;
            new Thread(() -> {
                myCache.get(temp + "");
            }, String.valueOf(i)).start();
        }
    }

}


/**
 * 自定义缓存加锁
 */
class MyCacheLock {

    private volatile Map<String, Object> map = new HashMap<>();

    //读写锁：更加细粒度的控制
    private ReentrantReadWriteLock readWriteLock = new ReentrantReadWriteLock();

    //存，写
    public void put(String key, Object value) {
        //写锁加锁
        readWriteLock.writeLock().lock();
        try {
            System.out.println(Thread.currentThread().getName() + "写入" + key);
            map.put(key, value);
            System.out.println(Thread.currentThread().getName() + "写入ok");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            //写锁解锁
            readWriteLock.writeLock().unlock();
        }

    }

    //取，读
    public void get(String key) {
        //读锁加锁
        readWriteLock.readLock().lock();
        try {
            System.out.println(Thread.currentThread().getName() + "读取" + key);
            Object o = map.get(key);
            System.out.println(Thread.currentThread().getName() + "读取ok");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            //读锁解锁
            readWriteLock.readLock().unlock();
        }
    }
}

/**
 * 自定义缓存
 */
class MyCache {

    private volatile Map<String, Object> map = new HashMap<>();

    //存，写
    public void put(String key, Object value) {
        System.out.println(Thread.currentThread().getName() + "写入" + key);
        map.put(key, value);
        System.out.println(Thread.currentThread().getName() + "写入ok");
    }

    //取，读
    public void get(String key) {
        System.out.println(Thread.currentThread().getName() + "读取" + key);
        Object o = map.get(key);
        System.out.println(Thread.currentThread().getName() + "读取ok");
    }
}
